So how should you make sense of sleep? Should you focus on recommendations for improving your memory? Managing your health status? Focusing on being in the best mood? New information is revealed every week about how sleep impacts our lives, which is good: offering improved insight into its effects on our lives, but simultaneously bad: as conflicting recommendations muddy our understanding about how to apply this information.

Naturally, not only is it important to know how sleeping habits can impact our lives, but we need to know how much sleep is required to make use of these benefits. If you took a Family Feud-style survey of 100 people to determine “ideal sleeping times”, it’s likely the most common responses would be 6 hours, 7 hours, or 8 hours per night. But factor in how our total sleep changes with seasonal changes, daylight levels, age, etc, and it is obviously more complicated than at first glance!

Consider Your Work

And I don’t mean “consider” as in how your work impacts your sleeping habits. Our work is a key element in building who we are, no matter how much we like to admit that. It is commonly our connection with what we do, the benefits to our lives that we can produce (including income), and the time we spend engrossed in our efforts that dictate, to some extent, how we live the rest of our lives.

With that in mind, perhaps it makes sense to look at sleep from this perspective: how do different amounts of sleep impact absenteeism from work — a study from Finland did just this in 2014. Presumably, people who miss work are less healthy, less productive, and sustain more injuries than those who do not.

This study (published in the academic journal “Sleep”) accessed a total sample of 1885 working males and 1875 working females, evaluating numerous factors such as total sleep, perceived lack of sleep as compared to their peers, overnight awakenings, early morning awakenings, ability to stay awake during the day, changes with seasonal variations, use of medications, among others. They were interested in finding out if “total sleep” time was related in some way to time missed from work as a result of “sickness absence”. (“Total sleep” was defined as all time spent sleeping during a 24-hour period — this would combine both overnight sleeping as well as daytime naps, no distinction was made between the two.)

What they found – How Much Sleep?

Signs of sleeping too little, such as waking up too early, being more tired than you peers, and using medications to aid sleeping were most consistently associated with sickness absence. Furthermore, the total amount of sleep created a “U-shaped” relationship for both men and women as it relates to time missed from work.

I’ll expand on this: For men, those getting 7.76 hours of sleep per day had the lowest risk of sickness absence at work, while for women, those getting 7.63 hours of sleep per day had the lowest risk. As people reported either less total sleep (eg. < 6 hours) or more total sleep (eg. > 9 hours), the risk of sickness absence at work increased for both genders.

So what does this mean for you? The authors provide this conclusion:

“The results highlight the need to focus on prevention of sleep disturbances and promotion of optimal sleep duration to help employees maintain their work ability and prevent sickness absence among both women and men”.

This research also suggests that staying within the range of 7-8 hours of sleep reduces the risk of a sickness related absence from work the most.

Caveats/Qualifiers/Limitations

Sleep research is highly diverse. For example, the definition of total sleep in this study was any sleep over a 24 hour period. In other research, only overnight sleep is considered, or overnight consistent sleep with no awakenings, or overnight sleep with no napping during the day, etc. With all this variability in definition, it becomes difficult to compare studies to each other or add results together as more information becomes available. Secondly, since this was a work-related study, the vast majority of those involved were of a younger age — the average age of men was 44.7 years and women 44.0 years. As already mentioned, sleeping patterns change with age, so the recommended 7-8 hours per night may be less applicable for people of older or younger ages. Finally, this study fails to distinguish reasons for work absences, only that there was a relationship between total sleep and work absence — the conclusions here do not suggest that having too little or too much sleep is the cause of more work absences, only that there is a relationship present.